1. The Field
This invention relates to capacitor electrolytes which have low resistivities and which provide low stable equivalent series resistance (ESR) during operation of aluminum electrolytic capacitors. More particularly, this invention relates to a phthalate electrolyte containing benzil which provides low ESR and low rates of change in ESR during operation of aluminum electrolytic capacitors.
2. Prior Teachings
There is a growing need for working electrolytes in low-voltage electrolytic capacitors that have low resistivities and provide low stable ESRs during operation of the capacitor. There is a limit to how low a resistivity in an electrolyte can be tolerated in a capacitor. The maximum operating voltage for an electrolytic capacitor is directly related to the electrolyte resistivity: in general, the lower the resistivity the lower the operating voltage.
Burger and Wu (Extended Abstracts of the Electrochemical Society #3, p. 13, May 1970) suggest that it should be possible to develop low voltage capacitors having low and stable ESR values by using very low resistivity working electrolytes (10 ohm-cm to 100 ohm-cm). Even at 10 ohm-cm this relationship predicts a sparking voltage (Vsp) of 260 V, and a capacitor with a 10 ohm-cm working electrolyte might reasonably be expected to operate effectively at a voltage as high as 100 V, and certainly at an applied voltage of 50 V.